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The British Astronomical Association ` ISSN 2631-4843 The British Astronomical Association Variable Star Section Circular No. 184 June 2020 Office: Burlington House, Piccadilly, London W1J 0DU Contents From the Director ....................................................................................................... 3 Summer Miras............................................................................................................ 3 Missing data from 1980-1995 – John Toone .............................................................. 6 Pulsating Star Programme – Shaun Albrighton .......................................................... 7 Report on the Long Period Variable Z Ursae Majoris using BAAVSS Archival Data – John Greaves .................................................................................... 9 Betelgeuse: the expected recovery happens – Mark Kidger ....................................... 14 Betelgeuse – A Century and more of Variation – Christopher Lloyd ........................... 22 CV & E News – Gary Poyner ..................................................................................... 28 Supernova 2020ue in NGC 4636 – Guy Hurst............................................................ 31 Spectrum of SN 2020hvf – David Boyd ...................................................................... 32 Eclipsing Binary News – Des Loughney ..................................................................... 33 Algol type eclipsing binary TX UMa. Can all sources have the correct period? – James Screech ............................................................................... 36 More observations of eclipsing binaries using the Open University COAST telescope – David Conner ............................................................................. 38 The evolution of the Hα double emission line during the total eclipse of the binary star system VV Cephei from 2017-19 – Jack Martin .............................. 42 Observations of the 2020 eclipse of the enigmatic binary EE Cephei – David Boyd ............................................................................................ 47 Section Publications ................................................................................................... 49 Contributing to the VSSC ........................................................................................... 49 Section Officers .......................................................................................................... 50 Cover Picture Corona Borealis and R CrB April 21, 2020. Canon 650D 55mm 6x60s © Nick Hewitt, Northampton UK 2 Back to contents From the Director Jeremy Shears Little did I know when I wrote this column for the last VSSC that I’d be preparing the next in the midst of a coronavirus lockdown. This has prevented gatherings across the country including, of course, our Section meeting which should have taken place on May 9. I am sure you were as disappointed as me that we could not meet. Apologies in particular to the speakers. We will reschedule for next year and make an announcement in due course. SUMMER MIRAS I was actually in India on a work assignment for the first 3 months of this year, when the pandemic started. I had to return a few days earlier than planned on the last British M = Max, m = min. Airways flight out of Bangalore before India stopped air travel completely. At the time of writing, my airfreight R Aqr M=Jly consignment is stuck there, including a few of my astronomy R Aql m=Jly/Aug books, telescope tripod and mount – and much of my V Cam M=Jun/Jly summer clothing. It was collected from my residence, but X Cam M=Jun/Jly was impounded at the airport when the restrictions came in. Whilst in Bangalore, I was able to connect with Professor G. m=Aug/Sep C. Anupama who is Dean of the Indian Institute of SU Cnc M=Aug/Sep Astrophysics and Professor-in-Charge of the Indian m=Jun Astronomical Observatory. She is also currently President of U CVn M=Jun the Astronomical Society of India. Her research interests RT CVn M=Jun/Jly include supernovae and cataclysmic variables, such as o Cet m=May/Jun novae and dwarf novae. I have suggested the VSS could R Com M=Jly/Aug help with any relevant projects she might have in the future. S CrB M=Jly/Aug Remarkably, the weather has been generally excellent up W CrB M=Jun and down the country since my return and I know many R Cyg m=May/Jun people have been making the most of the clear skies, with V Cyg M=Aug/Sep hardly any contrails, to get on with observing. One of the T Dra m=May/Jun benefits of being locked down at home, although I recognise SS Her M=Jun for many it will have been a struggle. I know that quite a few M=Jly/Aug people are using the time to analyse data and to write SU Lac M=Jun/Jly articles. RS Leo m=Jly/Aug Astronomy webinars in the time of corona W Lyn m=May/Jun X Oph m=May/Jun Naturally, all BAA meetings have been cancelled or R Ser M=May/Jun postponed in the meantime. To help maintain a sense of T UMa m=Aug/Sep community at a time when many of us are unable to leave home, the BAA has been organising a series of weekly Source BAA Handbook webinars at 7pm on Wednesdays. The presentations typically last for 15-30 minutes followed by questions from those attending. These are free to watch by everyone, whether a BAA Member or not. If you want to catch up on a webinar which has already been broadcast, recordings can be viewed on the BAA YouTube channel. Details of past and forthcoming webinars are available on the BAA website. I presented a webinar on “Two variable stars in the Northern Crown”, which was a general introduction to VS astronomy, with a focus on R CrB and T CrB. Tantalisingly, but very much on cue, R faded slightly a couple of days before transmission, but it subsequently brightened again. This occurrence did help to illustrate the point that stars do vary! You can watch the webinar here: https://www.youtube.com/watch?v=O4N9ewfnAKk. I was gratified to receive some enquiries about 3 Back to contents observing variables afterwards, with new observations following shortly after that. There is a lovely image of CrB on the cover of this circular, showing R, courtesy of Nick Hewitt. I highly commend to you the webinar “From Kitchens to Comets - Hunting for molecules with a spectroscope”, by Hugh Allen, Chairman of the Wells & Mendip Astronomers. This includes a panel discussion/Q&A with Hugh, David Boyd, Robin Leadbeater and Andy Wilson. See: https://www.youtube.com/watch?v=y6x1wuwKK20. I was also surprised to learn from John Mason’s webinar on Patrick Moore during the war years, just how many variable star observations Patrick made whilst on active service, even while flying in bombers! Note also that the Society for Astronomical Sciences is organising an online symposium jointly with AAVSO. The first session is on May 30, which is free, and there are 4 further session in June for which there is a fee. Details and programme here: https://socastrosci.z2systems.com/np/clients/socastrosci/event.jsp?event=27& More variables in the news Although lost from view for the season now, Betelgeuse has continued to receive much attention. In the last VSSC, Dr Mark Kidger wrote a fascinating piece about the recent fade of the star, which was read enthusiastically by many BAA Members, many of whom are not committed VS’ers. I am delighted that Mark continues his discussion on the star in the current circular, and we are treated to a further article by Chris Lloyd. Following the BBC News coverage of Betelgeuse and V Sge in the last few months, another variable object to receive attention on the BBC website was the blazar OJ 287. This fascinating system contains a binary black hole (BH): a supermassive BH of 18 billion solar masses being orbited by a ‘smaller’ BH of a mere 150 solar masses. It’s usually seen shining as a point source of light around magnitude 14.0-15.0. The reason why it hit the news is a publication in the Astrophysical Journal Letters on the Eddington flare caused by the impact of the secondary BH onto the accretion disk of the primary observed by Spitzer in July 2019. Gary Poyner has coordinated amateur observations of OJ 287 for many years and his summary of the latest findings can be read on the BAA website: https://britastro.org/node/21817 VSS campaigns on U Leo and HR Lyr A reminder that the campaign to observe the old nova U Leo continues: see the 2019 December BAA Journal and VSSC 182 for more details. Our band of observers has been expanding and I’d like to thank Stephen Arnold, Graham Darlington, Sjoerd Dufoer, Carlo Gualdoni, Paul Leyland, Michael Linnolt, Ken Menzies, Ian Miller, Roger Pickard, Jose Ripero, Richard Sabo, Dave Smith; also thanks to Boris Gänsicke who obtained spectroscopy on U Leo during March 2020 using the Isaac Newton Telescope. I presented an update on the VSS HR Lyr campaign which took place during the 2019/20 observing season in VSSC 183. A more detailed paper has now been submitted to the BAA Journal. Although the campaign is officially over, I hope observers will keep this star on their observing programme. It’s a good target to follow through the summer, autumn and well into next winter. John Toone clocks up 200,000! Hearty congratulations to John for making his 200,000th variable star observation. In John’s own words: “Last night (12th May) at 23:56 GMT I recorded my 200,000th visual magnitude estimate. In accordance with the VSS Director’s strict instruction it was of T CrB at mag 9.8. It was my 3,506th observation of T CrB since 2nd May 1981 which represents 25%
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